1. Technical Field
The disclosure generally relates to insulating glazing units and, more particularly, to a flexible spacer that is used to form thermal insulating laminates such as insulating glazing units which are used commercially as windows and doors or as parts of windows and doors.
2. Background Information
The procedure for assembling an insulating glazing unit generally involves spacing two sheets of glazing structures with a desiccated perimeter spacer that may be disposed inwardly from the outer edges of the glazing structures to define a channel that receives sealant. The glazed structures are typically glass sheets, but can also be plastic or other such suitable materials. One flexible spacer that is sold in the marketplace under the Federally Registered trademark SUPER SPACER includes a foam body, a foil moisture vapor barrier, and an acrylic adhesive disposed on its opposed sidewalls. The acrylic adhesive is used to connect the spacer to the glazing structures. A sealant material having a low moisture vapor transmission rate (MVTR) is arranged between the spacer and glazing structures to prevent or minimize the ingress of water vapor into the insulating chamber defined inwardly of the spacer and between the glazing structures. The primary sealant can be made from any self adhering material that has low gas and moisture permeability including polyisobutylene, saran, and epoxy adhesives.
An exemplary prior art insulating glazing unit is shown in FIGS. 1 and 2 to describe an exemplary environment wherein the spacer assembly configurations of the present disclosure may be used. The prior art insulating glazing unit is indicated by the reference numeral 2 and may be used in a variety of window and door applications for buildings and appliances. Insulating glazing unit 2 generally includes a spacer assembly 4 that supports a pair of glazing structures 6 in a spaced configuration to define an insulating chamber between glazing structures 6 and inwardly of spacer assembly 4. In the context of this application, the inward direction is toward the center of this insulating chamber while the outward direction is away from the center of the insulating chamber toward the atmosphere surrounding the insulating glazing unit. Glazing structures 6 are typically clear glass but also may be colored glass, plastic, polymer, or other materials. One or both of glazing structures 6 may be coated with a solar control or low emissivity coating. The insulating chamber is often filled with an insulating gas such as argon or krypton. For good thermal performance, where air or argon gas is used, the optimum spacing between glazing structures is about 12.5 mm.
Spacer assembly 4 includes at least a spacer body 10 and a primary sealant 12. Spacer body 10 typically, but optionally, carries a desiccant. Spacer body 10 is a flexible or semi-rigid foam material manufactured from thermoplastic or thermosetting plastics. Suitable thermosetting plastics include silicone and polyurethane. Silicone foam rubber is a common material for spacer body 10. Suitable thermoplastic materials include thermoplastic elastomers. The advantages of the silicone foam rubber include: good durability, minimal outgassing, low compression set, good resilience, high temperature stability and cold temperature flexibility. A further advantage of the silicone foam rubber is that the material is moisture permeable and so moisture vapor can easily reach the desiccant material within the foam. Spacer body 10 also may be made from cellular material which may be synthetic or naturally occurring. In the instance where the cellular material is composed of a naturally occurring material, cork and sponge may be suitable examples and in the synthetic version, suitable polymers including, but not limited to polyvinyl chlorides, polysilicone, polyurethane, polystyrene among others are suitable examples. Cellular material is desirable because such materials, while providing structural integrity additionally provide a high degree of interstices or voids between the material. In this manner, a high volume of air is included in the structure and when this is combined with an overall insulating material, the air voids complement the effectiveness of the insulation. When the choice of material is not cellular, any number of the high insulating materials known to have utility for the subject matter herein may be selected.
In the context of this application, the primary sealant is the material primarily responsible for preventing moisture vapor from entering chamber 8 between spacer body 10 and glazing structures 6 and preventing gas within chamber 8 from escaping. In this prior art example, spacer body 10 includes a moisture vapor barrier 14 so that primary sealant 12 is only required to seal the area where spacer body 10 is joined to glazing structures 6. Barrier 14 can be a metallic foil, a metallized polymer, or a polymer film having a low MVTR. Spacer assembly 4 optionally includes a secondary sealant 16. The gap between barrier 14 and the inner surface of each glazing structure 6 is sealed with primary sealant 12.
In the exemplary prior art configuration depicted in FIG. 2, spacer 10 also includes a thin acrylic adhesive 18 that is used to connected body 10 to glazing structures 6. Adhesive layer 18 is often 0.0762 mm (0.003 inches) to 0.127 mm (0.005 inches) thick and has a high moisture vapor transmission rate. Although acrylic adhesive 18 is used to form a relatively strong and fast pressure sensitive adhesive connection between spacer body 10 and glazing structure 6 at normal application temperatures, acrylic adhesive 18 has been found to lose adhesive strength at high temperatures and does not provide a significant moisture vapor barrier. Another drawback with the thin adhesive occurs when the faces of the spacer body are not square or when the spacer body varies in width along its length.